The present invention relates to comminuting machines in general, especially to roll crushers, and more particularly to improvements in comminuting machines of the type wherein a grate is movable to and from an operative position with reference to one or more toothed or analogous rotors.
It is well known to provide the rotor of a roll crusher with annuli of circumferentially extending teeth which cooperate with the teeth of a grate to break up bulky pieces of refuse, building material or the like. In many instances, the grate surrounds the underside and a second side of the rotor and has teeth extending into the spaces between the annuli of teeth on the rotor. Movability of the grate to and from an operative position with reference to the rotor is desirable and advantageous when the machine is to comminute bulky goods containing tough and/or readily flexible constituents which are likely to cling to the grate and to thereby interfere with proper comminution of next-following materials. Moreover, the constituents of the material to be comminuted are likely to damage the teeth and/or other parts of the grate so that the accessibility of such parts is important in order to avoid prolonged down times for replacement of damaged parts.
British Pat. No. 1,366,975 discloses a crusher which is used for the treatment of garbage and employs a grate disposed at one side of the rotor. The upper end portion of the grate is pivotably mounted in the housing of the crusher so that the grate can be swung to a position in which its teeth are spaced apart from the teeth of the rotor. The angle through which the grate is pivotable between its operative and inoperative positions is relatively small so that the accessibility of the grate upon movement to inoperative position is rather limited. Therefore, the removal of parts which cling to the grate and/or the repair work upon the grate is a tedious and time-consuming operation.
The situation is analogous when the comminuting machine comprises two rotors, i.e., the grate is normally pivotable about an axis which is located at the level of the one or the other rotor so that, when the grate is moved to the inoperative position, its toothed side is not readily accessible for all kinds of inspection, repair or cleaning work. An impact crusher wherein the pivot axis for the grate is located at the general level of the axis of the rotor is disclosed, for example, in British Pat. No. 1,249,738. In the machine of this patent, the grate is pivotable by an actuator means so as to move its lower portion away from the periphery of the rotor in order to change the comminuting action.
German Auslegeschrift No. 1,211,908 discloses a safety feature involving such mounting of the grate that the latter can yield when a piece of material which cannot be comminuted advances through the housing of the machine. Again, the pivot axis for the grate is located at the general level of the rotor axis, and the extent of angular movement of the grate about such axis is relatively small so that the toothed side of the grate is not readily accessible when it is held at a maximum distance from the periphery of the rotor.
German Pat. No. 704,853 discloses a grate which is pivotable about its lower end and is movable through a relatively small angle (of 45.degree. or less) between the operative and inoperative positions. Such pivoting of the grate is not sufficient to ensure convenient access to that side which is normally adjacent to the rotor. Similarly mounted grates are disclosed in German Pat. No. 450,481 and in U.S. Pat. No. 2,149,571.